Renal brush border membrane Na/Pi-cotransport: molecular aspects in PTH-dependent and dietary regulation

H Murer, M Lötscher, B Kaissling, M Levi… - Kidney international, 1996 - Elsevier
H Murer, M Lötscher, B Kaissling, M Levi, SA Kempson, J Biber
Kidney international, 1996Elsevier
Renal brush border membrane Na/P i-cotransport: Molecular aspects in PTH-dependent
and dietary regulation. Inorganic phosphate (P i) is reabsorbed in renal proximal tubules in a
sodium (Na)-dependent manner involving brush border Na/P i-cotransporter (s). Regulation
of renal P i reabsorption, such as by parathyroid hormone (PTH) and/or by dietary P i-
deprivation, involves alterations in the rate of Na/P i-cotransport. Two structurally different
Na/P i-cotransporters have been identified: type I-transporter and type II-transporter. The …
Renal brush border membrane Na/Pi-cotransport: Molecular aspects in PTH-dependent and dietary regulation. Inorganic phosphate (Pi) is reabsorbed in renal proximal tubules in a sodium (Na)-dependent manner involving brush border Na/Pi-cotransporter(s). Regulation of renal Pi reabsorption, such as by parathyroid hormone (PTH) and/or by dietary Pi-deprivation, involves alterations in the rate of Na/Pi-cotransport. Two structurally different Na/Pi-cotransporters have been identified: type I-transporter and type II-transporter. The related mRNAs and proteins are located in the proximal tubule and in the brush border membrane. In heterologous expression systems type I and type II Na/Pi-cotransporters mediate Na/Pi-cotransport. Characterization of the transport properties suggested that the type II transporter is ‘responsible’ for brush border membrane Na/Pi-cotransport (as observed in isolated vesicles). Administration of PTH to rats resulted in an inhibition of brush border membrane Na/Pi-cotransport (vesicles) and in a reduced brush border membrane content of the type II transporter. Feeding low Pi-diets resulted in an up-regulation of Na/Pi-cotransport (vesicles) and of type II transporter content; only after a prolonged exposure to low Pi-diets (more than 4 hr) was an increase in specific mRNA content observed. Refeeding high Pi diets had the opposite effects on Na/Pi-cotransport activity and on type II transporter protein. It is currently the task of future experiments to define the specific mechanisms leading to protein-synthesis-independent (PTH, acute Pi-deprivation, Pi-refeeding) and to protein-synthesis-dependent (prolonged Pi-deprivation) regulation of the type II Na/Pi-cotransporter.
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